Enzyme replacement therapy with laronidase (Aldurazyme, recombinant human a-L-iduronidase, EC 3.2.1.76) has been developed for MPS I, a lysosomal storage disorder. Laronidase given weekly into the vein helps many physical problems due to the disease, but does not treat the brain and spinal cord. The investigators purpose is to test delivery of laronidase given into the spinal fluid in patients with MPS I. The first aim is a pilot study of laronidase administered once per month into the spinal fluid for four months. Up to 10 study participants with spinal cord compression due to MPS will be studied. In the second aim, the treatment is continued every one to three months for a one-year extension period. The goals are to measure the safety and effectiveness of laronidase given into the spinal fluid to treat or stabilize spinal cord compression in the Hurler-Scheie and Scheie forms of MPS I. If successful, delivery into the spinal fluid could represent a practical, straightforward method of treating central nervous system disease due to lysosomal storage.